1. Field of the Invention
The present invention relates to methods for preparing a dough and/or baked product with a dehydrogenase.
2. Description of the Related Art
The strength of a dough is an important aspect of baking for both small-scale and large-scale applications. A strong dough has a greater tolerance of mixing time, proofing time, and mechanical vibrations during dough transport, whereas a weak dough is less tolerant to these treatments. A strong dough with superior rheological and handling properties results from flour containing a strong gluten network. Flour with a low protein content or a poor gluten quality results in a weak dough.
Dough "conditioners" are well known in the baking industry. The addition of conditioners to bread dough has resulted in improved machinability of the dough and improved texture, volume, flavor, and freshness (anti-staling) of the bread. Nonspecific oxidants, such as iodates, peroxides, ascorbic acid, potassium bromate and azodicarbonamide have a gluten strengthening effect. It has been suggested that these conditioners induce the formation of interprotein bonds which strengthen the gluten, and thereby the dough. However, the use of several of the currently available chemical oxidizing agents has been met with consumer resistance or is not permitted by regulatory agencies.
The use of enzymes as dough conditioners has been considered as an alternative to chemical conditioners. A number of enzymes have been used recently as dough and/or bread improving agents, in particular, enzymes that act on components present in large amounts in the dough. Examples of such enzymes are amylases, proteases, glucose oxidases, and (hemi)cellulases, including pentosanases.
The class of enzymes known as "oxidoreductases" (Class 1) is defined by the Nomenclature Committee of the International Union of Biochemistry on the Nomenclature and Classification of Enzymes (Enzyme Nomenclature, Academic Press, New York, 1992) as all enzymes which catalyze oxido-reductions. The substrate oxidized is regarded as a hydrogen or electron donor. The classification is based on `donor:acceptor oxidoreductase`. The recommended name is `dehydrogenase`. However, `oxidase` (EC 1.X.3.1) is used only for cases where O.sub.2 is acceptor, and `oxygenase` only for cases where the molecule O.sub.2 is directly incorporated into the substrate. `Peroxidase` is used specifically for enzymes using H.sub.2 O.sub.2 as acceptor (EC 1.11.X.Y).
Dehydrogenases typically catalyze the oxidation of a CH--OH, aldehyde, oxo, CH--NH.sub.2, CH--NH, CH--CH, sulphur, or heme (haem) group. Depending on the nature of the electron acceptor, this enzyme family can be divided into the following two sub-families: (1) NAD(P).sup.+ -dependent and (2) NAD(P).sup.+ -independent. The first group includes aliphatic/aromatic/carbohydrate alcohol:NAD(P).sup.+ dehydrogenases (such as xylose-1-dehydrogenase); and the second group includes donor:quinone dehydrogenases (such as cellobiose dehydrogenase), donor:cytochrome dehydrogenases (such as L-lactic dehydrogenase), and other dehydrogenases which use a disulphide compound or an iron-sulphur protein as an acceptor. Most NAD(P)-independent dehydrogenases (such as fructose dehydrogenase) use flavin compounds as their prosthetic groups, alone or in combination with a heme, although some dehydrogenases (such as glucose dehydrogenase EC 1.1.99.17) apparently do not employ flavin in their catalyses.
It is the object of the present invention to improve the properties of dough and/or baked products by the use of a dehydrogenase.